Hot rolled or cold rolled sheet metal - Langmuir Systems Forum

If you use hot rolled, a half hour bath in muriatic acid solution is enough to get rid of it (50:50 mix with water - you can add propylene glycol or isopropyl alcohol to keep it from freezing if that’s an issue). Then just rinse with water (you can also do a dip in a sodium carbonate - baking soda solution to counteract the acid but a good water wash is enough).

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You can get a plastic tub from a farm store like Tractor Supply or a small water “pond” from Home Depot that will hold the 2x2 stock we can fit on the Crossfire. You only need a few inches of solution - just lay the steel in the tray and have the solution cover it.

If you want to learn more, please visit our website Cold-Rolled Steel Plate.

The scale dissolves and you’ll have nice clean steel.

One thing though - keep your tray & solution covered. The fumes will attack any unprotected metal nearby. You should also use a respirator if you’re spending much time doing this. Always wear nitrile gloves.

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Not a stupid question at all. In fact many makers have been sorely disappointed in steel because of not knowing the difference. 416 stainless for instance can be had both ways. The surface looks better in cold rolled. I use it because it cleans up a little better in the milling vice. You have to be really careful with 440-c for instance. Hot rolled bar, is uglier on the surface. But is good stuff. There is a lot of sheared 440-c out there from cold rolled plate. It can have a very strong tractor tire tread grain when trying to finish. Seems that hot rolled is just a bit more dense. In steel going to be used forging, it probably doesn't matter. You can improve on the grain in cold rolled by forging, but hot rolled is damed good just as it comes form the mill. There is a lot of talk about grain refinement. It is mostly BS. You can get a shape that you want by forging with less metal that stock removal, But the grain refinement comes from the heat treating. Not from forging. Such things as edge packing, and breaking up the molecules is pure smoke and mirrors. Sells well to the UN educated. But is nothing more than Flem-flam at it's best. Mike "How it is made", prolly the best show ever made for gearheads,
had a segment on how they make steel. Wuz most excellent indeed.

Oftentimes you see a blacksmith forging a bar (making, say,
damascus), working with something like 1"x1"x10" bar.

Now, imagine that bar is 15 feet x 15 feet x 20 feet, being forged
by a gian press, while being held in giant tongs. That's what it looks
like.

Before that happens, they smelter iron and additives in a giant
smelter, with 3 giant electrodes. Must be megaAmps of current
doing the job. As the metal melts, they add alloying elements and
frequently check the resulting "mix" for proper percentages, adjusting
as needed. As they pour, filters will catch larger debri. Of course,
to qualify for NASA, this process needs to be pretty darn clean. It might
have to be repeated few times, to get progressively cleaner, better steel.


Some metals, like brass, can be hardened by "working" it . Steel doesn't
exhibit this feature. Still, when they roll, a lots of stress ends up in the
metal . Also, when hot rolling, exterior layers loose carbon and other alloying
elements. Nasty, hard scale forms. It has to be removed - this makes steel
"decarb" free and it also brings it down to exact dimensions (precision-ground) or just slightly oversized (called just that). Another way to remove the scale is to pickle the steel in acid, but of course it is not precise at all.

When using hot roll for removal-method knifes, one has to be careful not to end up with a warped blade, again due to the stress of hot-rolling being hidden in the metal bar. At best, you will have to spend lots of time orrecting it. Ok this was just on history channel and a while back how its made.

When steel is heated up the molecules align in to what they called a matrix. This becomes a stronger steel. In cold rolling they start with a huge billet of steel and run it throguh rollers compressing the steel. In cold roll steel youll have the same matrix as you did in the original billet (for the most part its really less change to the matrix). Cold rolling also uses many more rollers and or passes to get the stock to the final size and shape this is why it will tend to have a nicer looking finish.

With hot rolled steel the matrix will change become more dense and well aligned. In stock removal this is a good thing as it will grind and file etc smoother for us (more consitancy) than cold rolled. In the end though if your heat treating is good other than the ease of finishing both will end up the same or very close to the same in hardness grain structure etc.

Remember on raw hot rolled youll need to remove a portion of the mettal from top bottom and both esdges to get past the scale layer.

OT sort of but intresting. You know that alluminum foil you use to wrap your lunch in? Well it is a multi layer or damascus alloy. To get foil they use hot roller to thin out a very huge billet of aluminum. Once its at a given thickness it is folded in half and ran through the rollers again to increase its strength. Depending on how heavy a duty its to be used for it may be folded again and again ran through the rollers. So you heavy duty foil is folded twice giving a 4 layer damscus aluminum foil

Just a fun little fact i picked up watchign how its made heheh